The long-term goal of this research project is to assess the effects of cochlear implants on the development of speech production and language in congenitally deaf children with profound hearing loss. Current data indicate that pediatric cochlear implant users improve their speech and spoken language skills, but basic questions still remain regarding the optimum age for implantation, the relative advantages offered by cochlear implants vs. conventional hearing aids, and the development of speech and language in pediatric users of cochlear implants relative to that of children with normal hearing. To date, little research has been conducted on either the short-term or the long-term effects of implantation on speech and language before 1 year of age. In Aim 1, we will compare the speech and language skills of deaf children who receive cochlear implants in the first, second, third, or fourth year of life. Previous research has demonstrated that cochlear implants provide advantages over conventional hearing aids for at least some users; however, it is still unclear under what conditions this is true. In Aim 2, we will compare the speech and language skills of deaf children who received cochlear implants before age 4 to those of deaf children without cochlear implants who use conventional hearing aids. Finally, earlier ages at implantation, improved cochlear implant technology, and more effective habilitation programs have made development of speech and language skills by pediatric users of cochlear implants, comparable to those of children with normal hearing, a realistic possibility. In Aim 3, we will compare the speech and language skills of deaf children who received cochlear implants before age 4 to those of age-matched children with normal hearing. The three specific aims will be addressed in three projects examining the development of language (Project 1), speech articulation (Project 2), and speech intelligibility (Project 3). These three projects will be carried out using a longitudinal design involving a large sample of deaf children with cochlear implants, a comparison group of users of conventional hearing aids, and standard norms from children with normal hearing. Additionally, we will conduct a series of cross-sectional studies to examine more specific characteristics of the development of language, articulation, and speech intelligibility of deaf children with cochlear implants.